iPhone hacker extraordinaire Erica Sadun made an application for the iPhone that will listen to music and identify it! She writes –
Download a copy of the Listen beta. Itâ€™s still *very* beta. Install it on your iPhone, get near music and run it. It will sample the music for 5 seconds and then attempt to contact the id server. If it succeeds, great, youâ€™ll see the song, artist and album. If it fails, nothing happens. You just wait 30 seconds and if you havenâ€™t gotten an ID, quit and restart the program.